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printk: add interfaces for external access to the log buffer

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Add two new functions for reading the kernel log buffer.  The intention is for
them to be used by recovery/dump/debug code so the kernel log can be easily
retrieved/parsed in a crash scenario, but they are generic enough for other
people to dream up other fun uses.

[akpm@linux-foundation.org: buncha fixes]
Signed-off-by: Mike Frysinger <vapier@gentoo.org>
Cc: Robin Getz <rgetz@blackfin.uclinux.org>
Cc: Greg Ungerer <gerg@snapgear.com>
Cc: Russell King <rmk@arm.linux.org.uk>
Cc: Paul Mundt <lethal@linux-sh.org>
Acked-by: Tim Bird <tim.bird@am.sony.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Mike Frysinger 2007-10-16 23:26:43 -07:00 committed by Linus Torvalds
parent d823e3e754
commit 0b15d04af3
2 changed files with 58 additions and 0 deletions
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6
include/linux/kernel.h
View file

@ -172,6 +172,9 @@ asmlinkage int vprintk(const char *fmt, va_list args)
__attribute__ ((format (printf, 1, 0)));
asmlinkage int printk(const char * fmt, ...)
__attribute__ ((format (printf, 1, 2))) __cold;
extern int log_buf_get_len(void);
extern int log_buf_read(int idx);
extern int log_buf_copy(char *dest, int idx, int len);
#else
static inline int vprintk(const char *s, va_list args)
__attribute__ ((format (printf, 1, 0)));
@ -179,6 +182,9 @@ static inline int vprintk(const char *s, va_list args) { return 0; }
static inline int printk(const char *s, ...)
__attribute__ ((format (printf, 1, 2)));
static inline int __cold printk(const char *s, ...) { return 0; }
static inline int log_buf_get_len(void) { return 0; }
static inline int log_buf_read(int idx) { return 0; }
static inline int log_buf_copy(char *dest, int idx, int len) { return 0; }
#endif
unsigned long int_sqrt(unsigned long);

52
kernel/printk.c
View file

@ -219,6 +219,58 @@ static inline void boot_delay_msec(void)
}
#endif
/*
* Return the number of unread characters in the log buffer.
*/
int log_buf_get_len(void)
{
return logged_chars;
}
/*
* Copy a range of characters from the log buffer.
*/
int log_buf_copy(char *dest, int idx, int len)
{
int ret, max;
bool took_lock = false;
if (!oops_in_progress) {
spin_lock_irq(&logbuf_lock);
took_lock = true;
}
max = log_buf_get_len();
if (idx < 0 || idx >= max) {
ret = -1;
} else {
if (len > max)
len = max;
ret = len;
idx += (log_end - max);
while (len-- > 0)
dest[len] = LOG_BUF(idx + len);
}
if (took_lock)
spin_unlock_irq(&logbuf_lock);
return ret;
}
/*
* Extract a single character from the log buffer.
*/
int log_buf_read(int idx)
{
char ret;
if (log_buf_copy(&ret, idx, 1) == 1)
return ret;
else
return -1;
}
/*
* Commands to do_syslog:
*